Steering column and steering device

ABSTRACT

The outer column  25  has a front-side small-diameter tubular portion  37  into which the inner column  24  is press fitted. The inner-circumferential surface of the front-side small-diameter tubular portion  37  and the outer-circumferential surface of the inner column  24  come in contact with an interference fit at only a plurality of contact locations separated in the circumferential direction. At least one location in the axial direction of the column-side bracket  26  is welded to the outer-circumferential surface of the front-side small-diameter tubular portion  37  at only two weld locations that are close in the circumferential direction.

TECHNICAL FIELD

The present invention relates to a steering column having a function ofabsorbing an impact load at the time of a secondary collision, and asteering device provided with the steering column.

BACKGROUND ART

FIG. 23 illustrates an example of a steering device for an automobile. Asteering wheel 1 is attached to the rear-side end portion of a steeringshaft 2. The steering shaft 2 is rotatably supported on theinner-diameter side of a tubular steering column 3 supported by thevehicle body. The rotational motion of the steering wheel 1 istransmitted to a pinion shaft 7 of a steering gear unit 6 via thesteering shaft 2, a universal joint 4 a, an intermediate shaft 5, andanother universal joint 4 b. The rotational motion of the pinion shaft 7is converted into a linear motion of a rack shaft (not illustrated) ofthe steering gear unit 6. As a result, a pair of tie rods 8 is pushedand pulled, and a steering angle is applied to a pair of left and rightsteered wheels according to the amount of operation of the steeringwheel 1.

With respect to the steering device, the front-rear direction, the widthdirection, and the vertical direction are the front-rear direction, thewidth direction, and the vertical direction of the vehicle body to whichthe steering device is assembled.

FIGS. 24 to 26 illustrate a more specific structure of a steering deviceas described in JP 2013-136385A. This steering device has a function ofadjusting the height position of the steering wheel 1 attached to therear-side end portion of the steering shaft 2 a and a function ofabsorbing an impact load at the time of a secondary collision due to acollision accident of an automobile.

The steering column 3 a includes a tubular inner column 9 arranged onthe front side and a tubular outer column 10 arranged on the rear side.The rear-side portion of the inner column 9 is internally fitted intothe front-side portion of the outer column 10 by press fitting. Theinner column 9 has ridges 11 that protrude toward the outside in theradial direction and extend in the axial direction at four locations atequal intervals in the circumferential direction of theouter-circumferential surface of the rear-side portion. Theouter-circumferential surface of the inner column 9 comes in contactwith (fits with) the inner-circumferential surface of the outer column10 with an interference fit at only portions corresponding to the topportion of each ridge 11.

The front-side end portion of the inner column 9 is fixed to therear-side end portion of the gear housing 13 of an electric assistdevice 12 supported by the vehicle body. Therefore, the inner column 9is supported so as not to displace toward the front with respect to thevehicle body not only in the normal state but also during a secondarycollision. The gear housing 13 is supported with respect to the vehiclebody so as to be able to pivotally displace around a tilt shaft 14arranged in the width direction.

The steering column 3 a includes a column-side bracket 15 that is fixedto the outer column 10. The column-side bracket 15 has a U-shape andincludes a pair of side plate portions 16 arranged in parallel with eachother on both side portions in the width direction. The column-sidebracket 15 is fixed to the outer column 10 by welding the upper-endportions of the pair of side plate portions 16 to both side portions inthe width direction of the outer-circumferential surface of anintermediate portion in the axial direction of the outer column 10.

The steering column 3 a is supported by the vehicle body at anintermediate portion in the axial direction via a vehicle-body-sidebracket 17 and a clamp mechanism 18.

The vehicle-body-side bracket 17 includes a pair of support plateportions 19 arranged substantially parallel to each other at positionssandwiching the column-side bracket 15 from both sides in the widthdirection. The vehicle-body-side bracket 17 is supported so as to bedetachable toward the front with respect to the vehicle body due toimpact during a secondary collision.

The clamp mechanism 18 has a function of being able to switch between alocked state in which a pair of support plate portions 19 increases theforce for holding the column-side bracket 15 from both sides in thewidth direction to prevent the column side bracket 15 from beingdisplaced with respect to the vehicle-body-side bracket 17, and anunlocked state in which the force by which the pair of support plateportions 19 hold the column-side bracket 15 from both sides in the widthdirection is reduced or lost so as to allow the column side bracket 15to displace with respect to the vehicle-body-side bracket 17. In theunlocked state, the steering column 3 a pivotally displaces around thetilt shaft 14, so that the height position of the steering wheel 1 maybe adjusted. On the other hand, in the locked state, the steering wheelmay be held at the adjusted height position.

In the event of a collision accident, the impact load at the time of thesecondary collision causes the vehicle-body-side bracket 17 to detachtoward the front with respect to the vehicle body, so that the steeringwheel 1, a rear-side shaft 69 of the steering shaft 2 a, and the outercolumn 10 displace toward the front with respect to the inner column 9and the front-side shaft 70 of the steering shaft 2 a. At this time, theimpact load during the secondary collision is absorbed due to theouter-circumferential surface of the inner column 9 and theinner-circumferential surface of the outer column 10 sliding in theaxial direction.

In the steering device described above, the contact locations of theouter-circumferential surface of the inner column 9 with respect to theinner-circumferential surface of the outer column 10 are limited to theportions corresponding to the top portions of the ridges 11. In otherwords, at the time of a secondary collision, only the portions of theouter-circumferential surface of the inner column 9 corresponding to thetop portions of the ridges 11 slide in the axial direction with respectto the inner-circumferential surface of the outer column 10. Therefore,the inner column 9 and the outer column 10 may be stably slid in theaxial direction at the time of a secondary collision, and the absorptionperformance of the impact load may be stabilized.

CITATION LIST Patent Literature

Patent Literature 1: JP 2013-136385A

SUMMARY OF INVENTION Technical Problem

In the conventional structure illustrated in FIGS. 24 to 26, thecolumn-side bracket 15 fixed to the outer column 10 is arranged on theouter-diameter side of the press-fitted portion of the outer column 10where the inner column 9 is internally fitted by press-fitting. In acase of such a conventional structure, there is room for improvement asdescribed below.

In the conventional structure illustrated in FIGS. 24 to 26, aconfiguration is adopted in which the impact load at the time of asecondary collision is absorbed due to the inner column 9 and the outercolumn 10 sliding in the axial direction, and thus from the aspect ofsufficiently protecting the driver, it is important to keep the axialsliding resistance between the inner column 9 and the outer column 10,in other words, the press-fit load F of the inner column 9 with respectto the outer column 10 within an appropriate range.

In the conventional structure illustrated in FIGS. 24 to 26, thecolumn-side bracket 15 is fixed to the outer column 10 by welding.Therefore, when the column-side bracket 15 is fixed to the outer column10, the outer column 10 may be deformed due to residual stress generatedin the peripheral portion of the welded portion of the outer column 10.In particular, in the conventional structure illustrated in FIGS. 24 to26, the upper-end portions of the pair of side plate portions 16 of thecolumn-side bracket 15 are welded to the outer column 10 at two weldlocations that are largely separated in the circumferential direction.Therefore, the outer column 10 tends to be elliptically deformed so thatthe two welded portions are pulled toward both sides in the widthdirection due to the residual stress generated in the peripheral portionof the two welded portions.

In a case where the column-side bracket 15 fixed to the outer column 10is located on the outer-diameter side of the press-fitted portion of theouter column 10 as in the conventional structure illustrated in FIGS. 24to 26, the elliptical deformation as described above tends to occur inthe press-fitted portion. As a result, variation in the interference fitof the fitting portion between the inner column 9 and the outer column10 (the interference fit at the contact portions between the pluralityof ridges 11 of the inner column 9 and the inner-circumferential surfaceof the outer column 10) becomes large.

When the variation in the interference fit of the fitting portionbetween the inner column 9 and the outer column 10 becomes large, themanufacturing cost may become high due to reasons such as the timerequired for the work of selectively combining the inner column 9 andthe outer column 10 that is performed in order to keep the press-fittingload F of the inner column 9 with respect to the outer column 10 withinan appropriate range becoming long or the like.

An object of the present invention is to achieve a structure in whichthe sliding resistance in the axial direction of the inner column andthe outer column may be easily kept within an appropriate range.

Solution to Problem

The steering column of the present invention includes: a tubular outercolumn; a tubular inner column that is internally fitted and supportedinside the outer column; and a column-side bracket that is fixed bywelding to an outer-circumferential surface of the outer column.

The outer column has a press-fitted portion into which the inner columnis press-fitted to an inner-diameter side.

An inner-circumferential surface of the press-fitted portion and theouter-circumferential surface of the inner column come in contact witheach other with an interference fit directly or via another member atonly a plurality of contact locations separated in a circumferentialdirection.

At least one location of the column-side bracket is welded to theouter-circumferential surface of the press-fitted portion at only twoweld locations that are close in the circumferential direction.

In the steering column of the present invention, a configuration may beadopted in which the two weld locations exist within a circumferentialrange located between two contact locations adjacent in thecircumferential direction among the plurality of contact locations atpositions separated in the circumferential direction from the twocontact locations.

In the steering column of the present invention, a configuration may beadopted in which the inner column has ridges that protrude toward theoutside in the radial direction and extend in the axial direction at aplurality of locations separated in the circumferential direction of theouter-circumferential surface corresponding to the plurality of contactlocations, and only portions of the outer-circumferential surface of theinner column corresponding to the top portions of the ridges come intocontact with the inner-circumferential surface of the press-fittedportion with an interference fit.

In the steering column of the present invention, the column-side bracketmay include a connecting plate portion, a pair of side plate portionsthat are bent in a vertical direction from both end portions in thewidth direction of the connecting plate portion and sandwich the outercolumn from both sides in the width direction, and fixing plate portionsthat are bent toward the inside in the width direction from both endportions in a front-rear direction of the pair of side plate portions.

A configuration may be adopted in which, of the fixing plate portions, apair of fixing plate portions located on at least one side in thefront-rear direction of the column-side bracket are welded to theouter-circumferential surface of the press-fitted portion at the twowelding locations.

In the steering column of the present invention, each of the pair ofside plate portions may have an offset portion in an intermediateportion in the front-rear direction of a portion on an opposite side tothe connecting plate portion in the vertical direction that is offsettoward the inside in the width direction with respect to a surroundingportion thereof.

In the steering column of the present invention, the connecting plateportion may have a reinforcing rib extending in the width direction.

In the steering column-side bracket of the present invention, aconfiguration may be adopted in which the column-side bracket is made ofa metal plate, and a difference between a thickness dimension of themetal plate of the column-side bracket and a thickness dimension of thepress-fitted portion is 30% or less the thickness dimension of thepress-fitted portion.

The steering device of the present invention includes a steering column,a vehicle-body-side bracket, and a clamp mechanism.

The steering column includes the steering column of the presentinvention.

The vehicle-body-side bracket may have a pair of support plate portionsthat sandwich the outer column and the column-side bracket from bothsides in the width direction, and a tilt adjustment elongated holeformed in each of the pair of support plate portions and extends in thevertical direction, and is able to be supported by the vehicle body.

The clamp mechanism has an adjusting rod that is inserted in the widthdirection through the respective tilt adjustment elongated holes of thepair of support plate portions and the column-side bracket, and a pairof pressing portions that are arranged at both side portions in theaxial direction of the adjusting rod that protrudes toward the outsidein the axial direction of the pair of support plate portions, and thatby expanding or contracting the distance in the width directiontherebetween, are able to expand or contract the distance in the widthdirection between the pair of support plate portions.

In the steering device of the present invention, a configuration may beadopted in which the inner column is arranged on the front side of theouter column, and is supported with respect to the vehicle in a state inwhich the displacement toward the front is prevented.

Effect of Invention

With the present invention, it becomes easy to keep the slidingresistance in the axial direction of the inner column and the outercolumn within an appropriate range.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a side view of a steering device according to a first exampleof an embodiment of the present invention.

FIG. 2 is a cross-sectional view of section A-A in FIG. 1 in which apart is omitted.

FIG. 3 is a perspective view of the steering column and thevehicle-body-side bracket of the first example as viewed from the upperside and the rear side.

FIG. 4 is a perspective view of the steering column of the first exampleas viewed from the upper side and the rear side.

FIG. 5 is a perspective view of the steering column of the first exampleas viewed from the lower side and the rear side.

FIG. 6 is a perspective view of the steering column of the first exampleas viewed from the lower side and the front side.

FIG. 7 is a side view of the steering column of the first example.

FIG. 8 is a cross-sectional view of section B-B in FIG. 2 of thesteering column of the first example.

FIG. 9 is a cross-sectional view of section C-C in FIG. 7.

FIG. 10 is a perspective view of the inner column of the first exampleas viewed from the upper side and the rear side.

FIG. 11A is a view of the inner column and a mounting plate of the firstexample as viewed from the rear side, and FIG. 11B is an enlarged viewof portion Din FIG. 11A.

FIG. 12 is a side view of the vehicle-body-side bracket of the firstexample.

FIG. 13 is a partially enlarged view of FIG. 2 in which a part isomitted.

FIG. 14 is a perspective view of the steering column of a firstreference example related to the present invention as viewed from thelower side and the rear side.

FIG. 15 is a perspective view of the steering column illustrated in FIG.14 as viewed from the lower side and the front side.

FIG. 16 is a side view of the steering column illustrated in FIG. 14.

FIG. 17 is a view corresponding to section B-B in FIG. 2 of the steeringcolumn illustrated in FIG. 14.

FIG. 18 is a view of the steering column illustrated in FIG. 14 asviewed from the rear side.

FIG. 19 is a perspective view of the steering column of a second exampleof an embodiment of the present invention as viewed from the lower sideand the rear side.

FIG. 20 is a perspective view of the steering column of the secondexample as viewed from the lower side and the front side.

FIG. 21 is a side view of the steering column of the second example.

FIG. 22 is a view corresponding to section B-B in FIG. 2 of the steeringcolumn of the second example.

FIG. 23 is a perspective view illustrating an example of a conventionalstructure of a steering device.

FIG. 24 is a side view illustrating an example of a more specificstructure of the steering device.

FIG. 25 is a cross-sectional view of section E-E in FIG. 24 in which apart is omitted.

FIG. 26 is a cross-sectional view similar to FIG. 25 illustrating onlythe inner column and the outer column removed.

DESCRIPTION OF EMBODIMENTS First Example

A first example of an embodiment of the present invention will bedescribed with reference to FIGS. 1 to 13.

As illustrated in FIGS. 1 and 2, the steering device of this exampleincludes a steering shaft 20, a steering column 21, a vehicle-body-sidebracket 22, and a clamp mechanism 23.

The steering shaft 20 is rotatably supported on the inner-diameter sideof the tubular steering column 21. The steering wheel 1 (see FIG. 23)operated by the driver is attached to the rear-side end portion of thesteering shaft 20. The vehicle-body-side bracket 22, in a state of beingattached to the vehicle body, has a function of supporting anintermediate portion in the axial direction of the steering column 21with respect to the vehicle body. The clamp mechanism 23 has a functionof switching between an unlocked state that allows the steering column21 to displace in the vertical direction with respect to thevehicle-body-side bracket 22 in order that the height position of thesteering wheel 1 may be adjusted, and a locked state that prevents thesteering column 21 from displacing in the vertical direction withrespect to the vehicle-body-side bracket 22.

As illustrated in FIGS. 4 to 9, the steering column 21 of this exampleincludes an inner column 24 arranged on the front side, an outer column25 arranged on the rear side, and a column-side bracket 26 fixed to theouter column 25.

Each of the inner column 24 and the outer column 25 is a substantiallycylindrical member made of metal such as steel, aluminum or the like. Inthis example, each of the inner column 24 and the outer column 25 ismanufactured by a specified manufacturing method that includes a step ofchanging the inner-diameter dimension and the outer-diameter dimensionof a part in the axial direction of a raw pipe such as a drawn pipe orthe like as a raw material, and by subjecting the raw pipe to plasticworking such as hydroforming or drawing. In a case of implementing thepresent invention, each of the inner column 24 and the outer column 25may also be manufactured by other manufacturing methods such as castingor the like. In this example, the thickness dimension of the innercolumn 24 is substantially constant as a whole, and the thicknessdimension of the outer column 25 is substantially constant in theremaining portion excluding the rear-side end portion (bearing supportportion 42). The rear-side portion of the inner column 24 is internallyfitted into the front-side portion of the outer column 25 by pressfitting. In other words, the rear-side portion of the inner column 24 isinternally fitted in the front-side portion of the outer column 25 by aninterference fit.

The inner column 24 includes a cylindrical large-diameter tubularportion 27 and a cylindrical small-diameter tubular portion 28 that islocated further on the front side than the large-diameter tubularportion 27. The outer-diameter dimension of the small-diameter tubularportion 28 is smaller than the outer-diameter dimension of thelarge-diameter tubular portion 27. The front-side end portion of thelarge-diameter tubular portion 27 and the rear-side end portion of thesmall-diameter tubular portion 28 are connected by a conical tubularconnecting portion 29 having an outer-diameter dimension that decreasesgoing toward the front side.

The large-diameter tubular portion 27 has ridges 30 that protrude towardthe outside in the radial direction and extend in the axial direction ata plurality of locations (three or more locations) separated in thecircumferential direction of the outer-circumferential surface. Theoutside surface in the radial direction of each ridge 30 has a convexarc-shaped cross-sectional shape. In this example, the ridges 30 arearranged at four locations at equal intervals in the circumferentialdirection of the outer-circumferential surface of the large-diametertubular portion 27. Each of the ridges 30 exists in a range in the axialdirection in which the large-diameter tubular portion 27 is fitted tothe outer column 25 in the assembled state of the steering column 21;and more specifically, exists in a continuous range in the axialdirection corresponding to the rear-side end portion and intermediateportion in the axial direction of the large-diameter tubular portion 27.However, the range in the axial direction in which the ridge 30 existsmay extend further to the front side than in the structure of thisexample, and may be a wider range in the axial direction.

In this example, each of the ridges 30 is formed by plasticallydeforming a part of the large-diameter tubular portion 27 toward theoutside in the radial direction. Therefore, a concave groove extendingin the axial direction exists on the inner-circumferential surface sideof the large-diameter tubular portion 27 on the back-surface side ofeach of the ridges 30. As the plastic working for forming the ridges 30,for example, press working or the like may be adopted.

In this example, the height in the radial dimension H₃₀ of each ridge 30is set to 0.5% or more and 7% or less the outer-diameter dimension D₂₇of the location on the outer-circumferential surface of thelarge-diameter tubular portion 27 separated from the ridges 30 (FIG. 9).For example, in a case where the outer-diameter dimension D₂₇ of thelocation of the outer-circumferential surface of the large-diametertubular portion 27 separated from the ridges 30 is 38.5 mm, the radialheight dimension H₃₀ of the ridge 30 is set to 0.5 mm to 1.0 mm.

The inner column 24 is supported so as not to displace toward the frontwith respect to the vehicle body not only in the normal state but alsoduring a secondary collision. Therefore, the front-side end portion ofthe inner column 24 is connected and fixed to the rear-side end portionof a gear housing 32 of an electric assist device 31 supported by thevehicle body. The electric assist device 31 applies auxiliary powergenerated by an electric motor 33 as a power source to the steeringforce transmission path from the steering wheel 1 to the steered wheelsto reduce the force required for the driver to operate the steeringwheel 1. In this example, in order to enable adjustment of the heightposition of the steering wheel 1, the gear housing 32 is supported withrespect to the vehicle body so as to be able to pivotally displacearound the tilt shaft 34.

In this example, the steering column 21 further includes a mountingplate 35 for connecting and fixing the front-side end portion of theinner column 24 to the rear-side end portion of the gear housing 32. Themounting plate 35 is an annular flat plate member, and is externallyfitted and fixed to the front-side end portion of the small-diametertubular portion 28 of the inner column 24. The mounting plate 35 hasmounting holes 36 at a plurality of locations (three locations in theillustrated example) separated in the circumferential direction. On theother hand, the gear housing 32 has screw holes (not illustrated) atlocations on the rear-side end portion that are aligned with themounting holes 36 of the mounting plate 35. The front-side end portionof the inner column 24 is connected and fastened to the rear-side endportion of the gear housing 32 by inserting bolts (not illustrated) fromthe rear side through the mounting holes 36 of the mounting plate 35 andscrewing the bolts into the screw holes in the gear housing 32.

In this example, in a state where the front-side end portion of theinner column 24 is connected and fixed to the rear-side end portion ofthe gear housing 32, the phase of the arrangement in the circumferentialdirection of the mounting holes 36 provided in the mounting plate 35 inthe circumferential direction is regulated so that the positions in thecircumferential direction of the plurality of ridges 30 with respect tothe gear housing 32, or in other words, the positions in thecircumferential direction of the plurality of ridges 30 in the usedstate are uniquely determined. More specifically, the mounting holes 36are arranged at irregular intervals in the circumferential direction.

In this example, as illustrated in FIGS. 2 and 9, the positions in thecircumferential direction of the plurality of ridges 30 in the usedstate include positions at a total of four locations, such thatpositions at two locations are respectively shifted 45° toward bothsides in the circumferential from the upper-end portion, and positionsat two locations are respectively shifted 45° toward both sides in thecircumferential from the bottom-end portion.

The outer column 25 includes a cylindrical front-side small-diametertubular portion 37, a cylindrical large-diameter tubular portion 38located further on the rear side than the front-side small-diametertubular portion 37, and a rear-side small-diameter tubular portion 39located further on the rear side than the large-diameter tubular portion38. The inner-diameter dimension of the large-diameter tubular portion38 is larger than the inner-diameter dimension of both the front-sidesmall-diameter tubular portion 37 and the rear-side small-diametertubular portion 39. The front-side end portion of the large-diametertubular portion 38 and the rear-side end portion of the front-sidesmall-diameter tubular portion 37 are connected by a conical tubularfront-side connecting portion 40 having an inner-diameter dimension thatdecreases going toward the front side. The rear-side end portion of thelarge-diameter tubular portion 38 and the front-side end portion of therear-side small-diameter tubular portion 39 are connected by a conicaltubular rear-side connecting portion 41 having an inner-diameterdimension that decreases going toward the rear side.

The rear-side small-diameter tubular portion 39 has a bearing supportportion 42 in the rear-side half portion. The bearing support portion 42is a portion in which a rolling bearing (not illustrated) internallyfitted and supported in order to rotatably support the steering shaft 20(rear-side shaft 52) on the inner-diameter side of the outer column 25.The inner-diameter dimension of the bearing support portion 42 is largerthan the inner-diameter dimension of the front-side half portion of therear-side small-diameter tubular portion 39. Therefore, the thicknessdimension of the bearing support portion 42 is smaller than thethickness dimension of the front-side half portion of the rear-sidesmall-diameter tubular portion 39.

The large-diameter tubular portion 38 has a key lock hole 43 forinserting a lock pin of a steering lock mechanism at one location in thecircumferential direction of an intermediate portion in the axialdirection.

The front-side small-diameter tubular portion 37 is a press-fittingportion into which the rear-side portion of the inner column 24 isinternally fitted by press-fitting. In other words, in this example, theintermediate portion and the rear-side portion in the axial direction ofthe large-diameter tubular portion 27 that is the rear-side portion ofthe inner column 24 is internally fitted by press-fitting in thefront-side small-diameter tubular portion 37 that is the front-sideportion of the outer column 25. In this state, the outer-circumferentialsurface of the large-diameter tubular portion 27 is such that only theportions of the top portions of the ridges 30 come in contact with theinner-circumferential surface of the front-side small-diameter tubularportion 37 with an interference fit. In this example, the front-sidesmall-diameter tubular portion 37 is composed of a part of the raw pipethat is the raw material of the outer column 25.

The column-side bracket 26 is fastened to the outer column 25 in a statein which the column-side bracket 26 is arranged on the outer-diameterside (lower side) of the front-side portion of the front-sidesmall-diameter tubular portion 37, which is a portion of the outercolumn 25 to which the large-diameter tubular portion 27 of the innercolumn 24 is internally fitted by press-fitting.

The column-side bracket 26 is made by pressing a metal plate such assteel or the like, and includes a pair of side plate portions 44, aconnecting plate portion 45, and two fixing plate portions 46 for eachof the side plate portions 44. The pair of side plate portions 44 areseparated from each other in the width direction and arranged inparallel with each other. The connecting plate portion 45 connects thelower end portions of the pair of side plate portions 44 to each otherby connecting both end portions in the width direction to the lower endportions of the pair of side plate portions 44. In other words, the pairof side plate portions 44 are arranged so as to bend at right anglestoward the upper side from both end portions in the width direction ofthe connecting plate portions 45. The fixing plate portions 46 arearranged so as to be bent at right angles toward the inside in the widthdirection from an intermediate portion in the vertical direction of bothends in the front-rear direction of the side plate portions 44. The tipedge portions of the pair of fixing plate portions 46 arranged so as tobend at right angles toward the inside in the width direction from thefront-side end portions of the side plate portions 44 are close to eachother in the width direction. Moreover, the tip edge portions of thepair of fixing plate portions 46 arranged so as to bend at right anglestoward the inside in the width direction from the rear-side end portionsof the side plate portions 44 are close to each other in the widthdirection. In this example, the fixing plate portion 46 is configured bytwo pairs of fixing plate portions 46 arranged apart from each other inthe front-rear direction.

Each of the side plate portions 44 has a circular through hole 47 in thelower-side portion, and the through holes 47 are aligned with each otherin the width direction. Each of the side plate portions 44 has an offsetportion 48 in the middle portion in the front-rear direction of theupper-side portion. The offset portion 48 has a rectangular flat plateshape and is offset toward the inside in the width direction withrespect to the surrounding portion. Due to the presence of the offsetportion 48, the rigidity of the side plate portion 44 is increased.

The connecting plate portion 45 has a reinforcing rib 49. Thereinforcing rib 49 is formed in the middle portion in the front-reardirection of the connecting plate portion 45 over the entire length inthe width direction so as to extend in the width direction. Thereinforcing rib 49 has an arc-shaped cross-sectional shape with a convexupper side and a concave lower side. The rigidity of the connectingplate portion 45 is increased by the presence of the reinforcing rib 49.

Each of the fixing plate portions 46 has a substantially triangularshape in which the width dimension in the vertical direction becomessmaller going toward the inner side in the width direction, which is thetip-end side. The edge portion on the upper end of each tip-end portionof the fixing plate portion 46 has an arc shape along theouter-circumferential surface of the front-side small-diameter tubularportion 37 of the outer column 25 (see FIG. 13).

The column-side bracket 26 is fixed to the lower-side portion of thefront-side portion of the front-side small-diameter tubular portion 37of the outer column 25 by welding. In this example, in order to reducethe amount of deformation of the front-side small-diameter tubularportion 37 caused by welding, the welding location of the column-sidebracket 26 with respect to the front side small diameter cylinderportion 37 is devised.

In other words, only the edge portions on the upper ends of the tip-endportions of the fixing plate portions 46 of the column-side bracket 26are welded to the lower surface of the front-side small-diameter tubularportion 37 of the outer column 25 by weld bead portions 50.

In this example, there are two weld bead portions 50 for fixing thecolumn-side bracket 26 to the outer column 25 on each of both sides inthe front-rear direction of the column side bracket 26. On each of bothsides in the front-rear direction of the column-side bracket 26, the twoweld bead portions 50 are located symmetrically on both sides in thecircumferential direction that sandwich the lower-end portion of theouter column 25, and are close to each other in the circumferentialdirection. The space in the circumferential direction between these twoweld bead portions 50 is 15° or less (preferably 5° or less) whenrepresented by a center angle φ1 (see FIG. 9) centered on the centeraxis of the outer column 25. In this example, the circumferential rangein which these two weld bead portions 50 exist is 30° or less(preferably, 25° or less) when represented by a center angle φ2 (seeFIG. 9) centered on the center axis of the outer column 25.

In this example, the two weld bead portions 50 are arranged close toeach other in the circumferential direction on each of both sides of thecolumn-side bracket 26 in the front-rear direction. In other words, ofthe front-side small-diameter tubular portion 37 of the outer column 25,two locations (locations where the weld bead portions 50 exist) close toeach other in the circumferential direction are weld locations.Therefore, even in a case where the front-side small-diameter cylinderportion 37 is deformed such that the two locations are pulled to bothsides in the width direction due to residual stress generated in thesurrounding portions of the two locations after welding, it is difficultfor elliptical deformation to occur in the front-side small-diametertubular portion 37. In this example, the two welding points are close toeach other in the circumferential direction, and thus the deformation ofthe front-side small-diameter tubular portion 37 after welding is mostlythe same as in a case where there is only one welding location in thecircumferential direction. Therefore, the amount of deformation of thefront-side small-diameter tubular portion 37 after welding may bereduced.

In this example, on each of both sides in the front-rear direction ofthe column-side bracket 26, the two weld bead portions 50 exist in acircumferential range a (see FIG. 9) located at positions between twocontact portions of the contact portions between theinner-circumferential surface of the front-side small-diameter tubularportion 37 of the outer column 25 and the plurality of ridges 30 of theinner column 24 that are adjacent in the circumferential direction onthe lower half portion of the steering column 21, and that are separatedin the circumferential direction from the two contact portions.Therefore, it is possible to prevent or suppress the local deformationthat occurs around the welded portion of the front-side small-diametertubular portion 37 from extending to the portions of theinner-circumferential surface of the front-side small-diameter tubularportion 37 where the ridges 30 come in contact.

In this example, when the outer column 25 and the column side bracket 26are welded and joined by the weld bead portions 50, in order to be ableto adjust the positional relation between the outer column 25 and thecolumn-side bracket 26 (in particular, the vertical relationship, forexample, the vertical distance from the outer column 25 to the centeraxis of the pair of through holes 47 of the column side bracket 26, orthe like) as desired, a minute gap is provided as an adjustmentallowance between the edge portion of the top end of the tip-end portionof the fixing plate portions 46 and the outer-circumferential surface ofthe front-side small-diameter tubular portion 37. Therefore, in a casewhere the rigidity in the radial direction of the column-side bracket 26is higher than the rigidity in the radial direction of the front-sidesmall-diameter tubular portion 37, the front-side small-diameter tubularportion 37 tends to be attracted to the column-side bracket 26 based onthe existence of the minute gap at the time of welding joining by thewelding bead portions 50, and the amount of deformation of thefront-side small-diameter tubular portion 37 increases.

In this example, in order to reduce the amount of deformation of thefront-side small-diameter tubular portion 37 for such a reason, or morespecifically, in order to reduce the difference between the rigidity ofthe column side bracket 26 and the rigidity in the radial direction ofthe front-side small-diameter tubular portion 37, the thicknessdimension T₂₆ of the metal plate of the column-side bracket 26 and thethickness dimension T_(out) of the front-side small-diameter tubularportion 37 are made to be substantially equal to each other. Morespecifically, the difference between the thickness dimension of themetal plate of the column-side bracket 26 and the thickness dimension ofthe front-side small-diameter tubular portion 37 is made to be 30% orless (preferably, 15% or less) the thickness dimension of the front-sidesmall-diameter tubular portion 37.

With the column-side bracket 26 fixed to the outer column 25, theupper-side portions of the pair of side plate portions 44 are arrangedat positions that sandwich the front-side small-diameter tubular portion37 of the outer column 25 from both sides in the width direction. Inthis example, the upper-end portions of the pair of side plate portions44 are not welded to both side portions in the width direction of thefront-side small-diameter tubular portion 37 of the outer column 25. Inthis example, when welding and joining the outer column 25 and thecolumn-side brackets 26 by the weld bead portions 50, in order that thepositional relation between the outer column 25 and the column-sidebracket 26 (particularly, the positional relation in the widthdirection) can be adjusted as desired, and in order to prevent thedistance between the upper-side portions of the pair of side plateportions 44 from being expanded in the width direction by the front-sidesmall-diameter tubular portion 37 (to prevent the pair of side plateportions 44 from tilting), a minute gap as an adjustment allowance isprovided between each upper-side portion of the pair of side plateportions 44 and both side portions in the width direction of thefront-side small-diameter tubular portion 37 of the outer column 25 in astate of the steering column 21 alone.

As illustrated in FIG. 1, the steering shaft 20 includes a front-sideshaft 51 arranged on the front side and a rear-side shaft 52 arranged onthe rear side. The front-side shaft 51 and the rear-side shaft 52 arespline-fitted to enable torque transmission and relative displacement inthe axial direction.

The rear-side shaft 52 is supported by a rolling bearing (notillustrated) that is internally fitted in and supported by the bearingsupport portion 42 so as to only be able to rotate with respect to theouter column 25. A key lock collar (not illustrated) of the steeringlock mechanism is externally fitted and fixed to a location on therear-side shaft 52 aligned in the axial direction with the key lock hole43 of the outer column 25. The rear-side end portion of the rear-sideshaft 52 projects in the axial direction from the inner-diameter side ofthe outer column 25. The steering wheel 1 is attached to the rear-sideend portion of the rear-side shaft 52.

The front-side shaft 51 is supported by a rolling bearing (notillustrated) so as to only be able to rotate with respect to the innercolumn 24 and the gear housing 32. The front-side end portion of thefront-side shaft 51 projects in the axial direction from theinner-diameter side of the inner column 24, and is inserted inside thegear housing 32.

The vehicle-body-side bracket 22 is made of metal such as steel or thelike, and includes a mounting plate portion 53 and a pair of supportplate portions 54. The mounting plate portion 53 forms the upper-sideportion of the vehicle-body-side bracket 22, and is arranged in thewidth direction. The mounting plate portion 53 is supported by thevehicle body so as to be detachable toward the front by the impact atthe time of a secondary collision. The pair of support plate portions 54are arranged substantially parallel to each other at positionssandwiching the column-side bracket 26 from both sides in the widthdirection. The upper-end portion of each of the support plate portions54 is joined and fixed to an intermediate portion in the width directionof the mounting plate portion 53. Each of the support plate portions 54has a tilt adjustment elongated hole 55 extending in the verticaldirection at positions that are aligned with each other in the widthdirection and aligned with the through holes 47 of the column-sidebracket 26. Each of the tilt adjustment elongated holes 55 has an arcshape centered on the tilt shaft 34.

In this example, as illustrated in FIGS. 12 and 13, each of the supportplate portions 54 has a substantially rectangular flat plate-shapedoffset portion 56 offset toward the inside in the width direction withrespect to the surrounding portion in an intermediate portion in thefront-rear direction. The tilt adjustment elongated hole 55 is formed soas to penetrate the lower-side portion of the offset portion 56 in thewidth direction. The rigidity of each of the support plate portions 54is increased by the presence of the offset portion 56.

As illustrated in FIG. 12, the offset portion 56 is arranged at aposition facing the side plate portion 44 of the column-side bracket 26in the width direction.

As illustrated in FIG. 2, the clamp mechanism 23 includes an adjustingrod 58, an adjusting nut 59, a cam device 60, an adjusting lever 61, anda thrust bearing 62.

The adjusting rod 58 is inserted in the width direction through a pairof tilt adjustment elongated holes 55 and a pair of through holes 47.The adjusting rod 58 has a head portion 63 at a base-end portion(left-end portion in FIG. 2) and a male screw portion 64 at the tip-endportion (right-end portion in FIG. 2). The adjusting nut 59 is screwedinto the male screw portion 64. The cam device 60 is arranged betweenthe head portion 63 and the support plate portion 54 on one side (leftside in FIG. 2). The cam device 60 has a drive-side cam 65 located onthe outside in the width direction and a driven-side cam 66 located onthe inside in the width direction. The base-end portion of the adjustinglever 61 is fixed to the drive-side cam 65. The driven-side cam 66engages with the tilt adjustment elongated hole 55 of one of the supportplate portions 54 so that there is no relative rotation. When thedrive-side cam 65 and the driven-side cam 66 are relatively rotated byswinging the adjusting lever 61 around the adjusting rod 58, due to thepressing of the side surfaces (cam surfaces) of the drive-side cam 65and the driven-side cam 66 that face each other, the dimension in theaxial direction of the cam device 60 expands or contracts. In thisexample, in a case where the adjusting lever 61 is swung in a specifieddirection, the dimension in the axial direction of the cam device 60 isincreased, and in a case where the adjusting lever 61 is swung in adirection opposite the specified direction, the dimension in the axialdirection of the cam device 60 is reduced. The thrust bearing 62 isarranged between the adjusting nut 59 and the other support plateportion 54 (right one in FIG. 2).

When adjusting the height position of the steering wheel 1, the clampmechanism 23 is set to the unlocked state by swinging the adjustinglever 61 in a specified direction. In other words, when the adjustinglever 61 is swung in a specified direction (for example, downward), thedimension in the axial direction of the cam device 60 is reduced, andthe space between the driven-side cam 66 and the thrust bearing 62 iswidened. As a result, the frictional force acting between the inner sidesurface in the width direction of the pair of support plate portions 54and the outer side surface in the width direction of the pair of sideplate portions 44 is reduced or lost, and the column-side bracket 26 isin an unlocked state in which displacement of the column-side bracket 26with respect to the vehicle-body-side bracket 22 is possible. In thisunlocked state, by pivotally displacing the steering column 21 acentered about the tilt shaft 34, the adjusting rod 58 is able to moveinside the pair of tilt adjustment elongated holes 55, and the heightposition of the steering wheel 1 may be adjusted.

After adjusting the height position of the steering wheel 1, by swingingthe adjusting lever 61 in the direction opposite to the specifieddirection (for example, upward), the clamp mechanism 23 is set to thelocked state. In other words, when the adjusting lever 61 is swung inthe direction opposite to the specified direction, the dimension in theaxial direction of the cam device 60 is increased, and the distancebetween the driven-side cam 66 and the thrust bearing 62, which is apair of pressing portions, is shortened, and as a result, the distancebetween the pair of support plate portions 54 is reduced. As a result,the frictional force acting between the inner side surface in the widthdirection of the pair of support plate portions 54 and the outer sidesurface in the width direction of the pair of side plate portions 44 isincreased, and the column-side bracket 26 is in a locked state in whichdisplacement of the column-side bracket 26 with respect to thevehicle-body-side bracket 22 is not possible. In this locked state, thesteering wheel 1 is held at the adjusted height position.

In this example, the welding locations of the column-side bracket 26with respect to the outer column 25 are two locations (where the weldbead portions 50 exist) close to each other in the circumferentialdirection on each of both sides of the column-side bracket 26 in thefront-rear direction. Moreover, in the state of the steering column 21alone, there is a minute gap between each upper-side portion of the pairof side plate portions 44 and both side portions in the width directionof the front-side small-diameter tubular portion 37 of the outer column25. However, in the structure of this example, regardless of theexistence of such a minute gap, the support rigidity in the widthdirection of the column-side bracket 26 and the outer column 25 by thepair of support plate portions 54 may be sufficiently ensured in thelocked state.

In the structure of this example, when the distance between thedriven-side cam 66 and the thrust bearing 62 is shortened due toswinging of the adjusting lever 61 when setting the locked state, aninward load P in the width direction acts on the outer-side surfaces ofthe pair of support plate portions 54 from both the driven-side cam 66and the thrust bearing 62. As a result, first, each of the pair ofsupport plate portions 54 swings toward the inside in the widthdirection with the upper-end portion as the center. Then, the inner-sidesurface of each of the lower-side portions of the pair of support plateportions 54 comes in contact with the outer-side surface of each of thelower-end portions of the pair of side plate portions 44 of thecolumn-side bracket 26. The location of this contact becomes a firstfulcrum S1. In the structure of this example, the connecting plateportion 45 that connects the lower-end portions of the pair of sideplate portions 44 has a reinforcing rib 49 at an intermediate portion inthe front-rear direction, and the rigidity is enhanced by thereinforcing rib 49. Therefore, the load applied to the first fulcrum S1from each of the pair of support plate portions 54 may be sufficientlysupported by the connecting plate portion 45.

Next, due to the action of the load P, each of the pair of support plateportions 54 is elastically deformed such that the inside in the widthdirection becomes convex as illustrated by the thick broken line in FIG.13. Then, the inner-side surface of each of the upper-side portions ofthe pair of support plate portions 54 comes in contact with theouter-side surface of each of the upper-side portions of the pair ofside plate portions 44 of the column-side bracket 26. As a result, theupper-side portions of the pair of side plate portions 44 are displacedtoward the inside in the width direction. Then, the inner side surfacesof each upper-side portions of the pair of side plate portions 44 (innerside surfaces of the offset portions 48) come in contact with both sidesurfaces in the width direction of the front-side small-diameter tubularportion 37 of the outer column 25. In other words, the minute gapsexisting between the upper-side portions of the pair of side plateportions 44 and both side portions in the width direction of thefront-side small-diameter tubular portion 37 of the outer column 25disappear. In this state, the contact portion between the inner-sidesurface of the upper-side portions of the pair of support plate portions54 and the outer-side surfaces of the upper-side portions of the pair ofside plate portions 44 of the column-side bracket 26 becomes a secondfulcrum S2. In the structure of this example, each of the pair of sideplate portions 44 has an offset portion 48 that is offset toward theinside in the width direction with respect to the surrounding portion inan intermediate portion in the front-rear direction of the upper-sideportion. Therefore, the rigidity of each of the pair of side plateportions 44 may be increased based on the presence of the offsetportions 48, and as a result, each of the pair of side plate portions 44is suppressed from being elastically deformed in a direction illustratedby the thick broken line in FIG. 13. Moreover, of the inner-sidesurfaces of the pair of side plate portions 44, the locations that comein contact with both side surfaces in the width direction of thefront-side small-diameter tubular portion 37 of the outer column 25 maybe limited to the inner-side surfaces of the offset portion 48.Therefore, the inner-side surfaces of the pair of side plate portions 44may be accurately brought into contact with both side surfaces in thewidth direction of the front-side small-diameter tubular portion 37 ofthe outer column 25 over a specified contact area. In the structure ofthis example, the front-side small-diameter tubular portion 37 of theouter column 25 is composed of a part of the raw pipe which is the rawmaterial of the outer column 25. The outer-circumferential surface ofthe raw pipe is a cylindrical surface having high shape accuracy(roundness). Therefore, also by this, the inner side surfaces of theoffset portions 48 of the pair of side plate portions 44 are accuratelybrought into contact with both side surfaces in the width direction ofthe front-side small-diameter tubular portion 37 of the outer column 25with a specified contact area.

As described above, in the structure of this example, in the lockedstate, the minute gaps existing between the upper-side portions of thepair of side plate portions 44 and both side portions in the widthdirection of the front-side small-diameter tubular portion 37 of theouter column 25 disappear, and there are a total of four fulcrums, twolower-side first fulcrums S1 and two upper-side second fulcrums S2,between the pair of support plate portions 54 and the column-sidebracket 26. As a result, it is possible to sufficiently secure thesupport rigidity in the width direction of the column-side bracket 26and the outer column 25 by the pair of support plate portions 54.

When an automobile has a collision accident and a secondary collisionoccurs in which the driver's body collides with the steering wheel 1, animpact load toward the front is applied to the outer column 25 and thevehicle-body-side bracket 22 from the steering wheel 1 via the rear-sideshaft 52. Due to this impact load, the vehicle-body-side bracket 22 isdetached toward the front with respect to the vehicle body, and theouter column 25, the rear-side shaft 52, and the steering wheel 1displace toward the front with respect to the inner column 24 and thefront-side shaft 51. At this time, the impact load at the time of thesecondary collision is absorbed due to sliding in the axial direction ofthe outer-circumferential surface of the large-diameter tubular portion27 of the inner column 24 and the inner-circumferential surface of thefront-side small-diameter tubular portion 37 of the outer column 25.

In this example, the contact locations of the outer-circumferentialsurface of the large-diameter tubular portion 27 of the inner column 24with the inner-circumferential surface of the front-side small-diametertubular portion 37 of the outer column 25 are limited to the portionscorresponding to the respective top portions of the ridges 30. In otherwords, at the time of the secondary collision, of theouter-circumferential surface of the large-diameter tubular portion 27of the inner column 24, only the portions corresponding to the topportions of the ridges 30 slide in the axial direction with theinner-circumferential surface of the front-side small-diameter tubularportion 37 of the outer column 25. Therefore, at the time of a secondarycollision, the outer-circumferential surface of the large-diametertubular portion 27 of the inner column 24 and the inner-circumferentialsurface of the front-side small-diameter tubular portion 37 of the outercolumn 25 are able to stably slide in the axial direction, andabsorption performance of the impact load may be stabilized.

The steering device of this example absorbs the impact load at the timeof the secondary collision due to sliding in the axial direction of theouter-circumferential surface of the inner column 24 and theinner-circumferential surface of the outer column 25, and thus from theaspect of sufficiently protecting the driver, it is important to keepthe resistance in the axial direction between the inner column 24 andthe outer column 25, or in other words, the press-fitting load F of theouter-circumferential surface of the inner column 24 with respect to theinner-circumferential surface of the outer column 25 within anappropriate range. In this regard, in the steering device of thisexample, it is easy to keep the press-fitting load F of theouter-circumferential surface of the inner column 24 with respect to theinner-circumferential surface of the outer column 25 within anappropriate range.

In the structure of this example, the front-side small-diameter tubularportion 37 of the outer column 25 is composed of a part of the raw pipewhich is the raw material of the outer column 25. Theinner-circumferential surface of the raw pipe is a cylindrical surfacehaving a highly accurate shape (roundness) and small variation in theinner-diameter dimension. Therefore, the inner-circumferential surfaceof the front-side small-diameter tubular portion 37 is also acylindrical surface having highly accurate shape and small variation inthe inner-diameter dimension. Accordingly, it is possible to reducevariation in the interference λ of the fitting portion between thelarge-diameter tubular portion 27 of the inner column 24 and thefront-side small-diameter tubular portion 37 of the outer column 25,which is the interference at the contact portions between theinner-circumferential surface of the front-side small-diameter tubularportion 37 and the plurality of ridges 30, by that amount.

In the structure of this example, the amount of deformation of thefront-side small-diameter tubular portion 37 due to welding of thecolumn-side bracket 26 to the front-side small-diameter tubular portion37 of the outer column 25 may be reduced. Therefore, it is possible toreduce the amount of increase in the variation in the interference λ ofthe fitting portion between the large-diameter tubular portion 27 of theinner column 24 and the front-side small-diameter tubular portion 37 ofthe outer column 25 caused by such deformation.

Accordingly, in the structure of this example, it is not necessary tomake the accuracy of the inner column 24 and the outer column 25excessively high in order to keep the press-fitting load F within anappropriate range. Moreover, in order to keep the press-fitting load Fwithin an appropriate range, the work of selectively combining the innercolumn 24 and the outer column 25 becomes unnecessary, or even in a casewhere this work is necessary, the work time may be shortened. Therefore,the manufacturing cost of the steering device may be kept low.

Reference Example

A reference example related to the present invention will be describedwith reference to FIGS. 14 to 18.

In this reference example, the outer column 25 a of the steering column21 a includes a cylindrical front-side large-diameter tubular portion 67that is positioned further on the front side than the front-sidesmall-diameter tubular portion 37 a. The inner-diameter dimension of thefront-side large-diameter tubular portion 67 is larger than theinner-diameter dimension of the front-side small-diameter tubularportion 37 a. The rear-side end portion of the front-side large-diametertubular portion 67 and the front-side end portion of the front-sidesmall-diameter tubular portion 37 a are connected by a conical tubularconnecting portion 68 having an inner-diameter dimension that increasesgoing toward the front side. The inner-circumferential surface of thefront-side large-diameter tubular portion 67 and theinner-circumferential surface of the connecting portion 68 are not incontact with the plurality of ridges 30 of the inner column 24. In otherwords, in this reference example, as in the first example, thelarge-diameter tubular portion 27 of the inner column 24 is press-fittedonly into the front-side small-diameter tubular portion 37 a of theouter column 25 a. The plurality of ridges 30 of the inner column 24 arein contact in a state in which there is interference only with theinner-circumferential surface of the front-side small-diameter tubularportion 37 a of the inner-circumferential surface of the outer column 25a.

The position in the axial direction of the front-side large-diametertubular portion 67 of the outer column 25 a coincides with the positionin the axial direction of the front-side end portion of the column-sidebracket 26 a. The position in the axial direction of the front-side endportion of the large-diameter tubular portion 38 a of the outer column25 a coincides with the position in the axial direction of the rear-sideend portion of the column-side bracket 26 a. Each of the fixing plateportions 46 a of the column-side bracket 26 a has a shorter dimension inthe width direction than in the case of the first example. The inner endportions in the width direction, which are the respective tip-endportions of the fixing plate portions 46 a, are positioned below bothside portions in the width direction of the outer column 25 a.

In this reference example as well, as in the first example, in order tofix the column-side bracket 26 a to the outer column 25 a, only the edgeportions on the upper ends of the tip-end portions of the fixing plateportions 46 a of the column-side bracket 26 a are welded and joined tothe lower surface of outer column 25 by weld bead portions 50. However,in this reference example, the positions of the weld bead portions 50,which are welded portions, are different from those of the firstexample.

In this reference example, the edge portions of the upper ends of thetip-end portions of the pair of fixing plate portions 46 a located onthe front side of the column-side bracket 26 a are welded and joined tothe lower surface of both side portions in the width direction of thefront-side large-diameter tubular portion 67 of the outer column 25 a byweld bead portions 50. The edge portions of the upper ends of thetip-end portions of the pair of fixing plate portions 46 a located onthe rear side of the column-side bracket 26 a are welded and joined tothe lower surfaces of both side portions in the width direction of thefront-side end portion of the large-diameter tubular portion 38 of theouter column 25 a by the weld bead portions 50.

In this reference example, the welded locations of the column-sidebracket 26 a with respect to the outer column 25 a are portions(front-side large-diameter tubular portion 67, front-side end portion ofthe large-diameter tubular portion 38) of the outer column 25 a that areseparated in the axial direction from the portion (front-sidesmall-diameter tubular portion 37 a) in which the inner column 24 ispress fitted. Therefore, it is possible to prevent or suppress thedeformation of the outer column 25 a due to welding from reaching theportion (front-side small-diameter tubular portion 37 a) of the outercolumn 25 a in which the inner column 24 is press-fitted. Therefore, itis possible to suppress the amount of increase in the variation in theinterference λ of the fitting portion between the large-diameter tubularportion 27 of the inner column 24 and the front-side small-diametertubular portion 37 a of the outer column 25 a caused by the deformation.Accordingly, it becomes easy to keep the press-fitting load F on theouter-circumferential surface of the large-diameter tubular portion 27of the inner column 24 with respect to the inner-circumferential surfaceof the front-side small-diameter tubular portion 37 a of the outercolumn 25 a within an appropriate range by that amount.

In this reference example, on each of both sides in the front-reardirection of the column-side bracket 26 a, the distance in thecircumferential direction between the two weld bead portions 50 islarger than in the case of the first example. Therefore, the supportrigidity of the column-side bracket 26 a with respect to the outercolumn 25 a may be increased.

As a modification of this reference example, two weld bead portions maybe arranged close to each other in the circumferential direction as inthe first example on at least one side of both sides in the front-reardirection of the column-side bracket. In this case, the amount ofdeformation of the outer column due to welding on the at least one sidemay be made smaller than in the case of this reference example.Accordingly, the amount of increase in the variation in the interferenceλ of the fitting portion between the inner column and the outer columncaused by such deformation may be made smaller. Other configurations andoperational effects are the same as in the first example.

Second Example

A second example of an embodiment of the present invention will bedescribed with reference to FIGS. 19 to 22.

In this example, the configuration of the front-side end portion of theouter column 25 b of the steering column 21 b, the configuration of thepair of fixing plate portions 46 a located on the front side of thecolumn-side bracket 26 b, and the configuration relating to weldedjoints of the pair of fixing plate portions 46 a located on the frontside of the column-side bracket 26 b with respect to the front-side endportion of the outer column 25 b are the same as in the referenceexample.

In other words, the outer column 25 b includes a front-sidelarge-diameter tubular portion 67 and a connecting portion 68 similar tothose in the reference example at the front-side end portion. Each ofthe pair of fixing plate portions 46 a located on the front side of thecolumn-side bracket 26 b has a shorter dimension in the width directionthan in the case of the first example. The edge portions of the upperends of the tip-end portions of the pair of fixing plate portions 46 alocated on the front side of the column-side bracket 26 b are welded andjoined to the lower surfaces of both side portions in the widthdirection of the front-side large-diameter tubular portion 67 of theouter column 25 b by the weld bead portions 50.

The other configurations are the same as in the first example. In otherwords, in this example, the pair of fixing plate portions 46 located onthe rear side of the column-side bracket 26 b is welded and joined tothe lower surface of the front-side small-diameter tubular portion 37 ofthe outer column 25 b by weld bead portions 50 that are close to eachother in the circumferential direction.

In the structure of this example, the distance in the circumferentialdirection between the two weld bead portions 50 on the front side of thecolumn-side bracket 26 b is larger than that in the case of the firstexample. Therefore, the support rigidity of the column-side bracket 26 bwith respect to the outer column 25 b may be increased as compared withthe case of the first example. The dimension in the axial direction ofthe front-side small-diameter tubular portion 37, which is the portionof the outer column 25 a where the inner column 24 is internally fittedby press fitting, is larger than that in the reference example.Therefore, the impact absorption stroke at the time of the secondarycollision may be made longer than that in the case of the referenceexample. The other operational effects are the same as those of thefirst example and the reference example.

The structure of each example of an embodiment of the present inventionand the structure of the reference example may be appropriately combinedand implemented as long as there is no contradiction.

In a case of implementing the present invention, a configuration may beadopted in which the column-side bracket is arranged on the upper sideof the portion of the outer column into which the inner column ispress-fitted.

In a case of implementing the present invention, a configuration may beadopted in which the inner-circumferential surface of the outer columnand the outer-circumferential surface of the inner column come incontact in a state in which there is interference fit via another memberat only a plurality of locations that are separated in thecircumferential direction. In this case, as the other member, a metalwire material or the like arranged in the axial direction may be usedfor example.

REFERENCE SIGNS LIST

-   -   1 Steering wheel    -   2, 2 a Steering shaft    -   3, 3 a Steering column    -   4 a, 4 b Universal joint    -   5 Intermediate shaft    -   6 Steering gear unit    -   7 Pinion shaft    -   8 Tie rod    -   9 Inner column    -   10 Outer column    -   11 Ridge    -   12 Electric assist device    -   13 Gear housing    -   14 Tilt shaft    -   15 Column-side bracket    -   16 Side plate portion    -   17 Vehicle-body-side bracket    -   18 Clamp mechanism    -   19 Support plate portion    -   20 Steering shaft    -   21, 21 a, 21 b Steering column    -   22 Vehicle-body-side bracket    -   23 Clamp mechanism    -   24 Inner column    -   25, 25 a, 25 b Outer column    -   26, 26 a, 26 b Column-side bracket    -   27 Large-diameter tubular portion    -   28 Small-diameter tubular portion    -   29 Connecting portion    -   30 Ridge    -   31 Electric assist device    -   32 Gear housing    -   33 Electric motor    -   34 Tilt shaft    -   35 Mounting plate    -   36 Mounting hole    -   37, 37 a Front-side small-diameter tubular portion    -   38, 38 a Large-diameter tubular portion    -   39 Rear-side small-diameter tubular portion    -   40 Front-side connecting portion    -   41 Rear-side connecting portion    -   42 Bearing support portion    -   43 Key lock hole    -   44 Side plate portion    -   45 Connecting plate portion    -   46, 46 a Fixing plate portion    -   47 Through hole    -   48 Offset portion    -   49 Reinforcing rib    -   50 Weld bead portion    -   51 Front-side shaft    -   52 Rear-side shaft    -   53 Mounting plate portion    -   54 Support plate portion    -   55 Tilt adjustment elongated hole    -   56 Offset portion    -   58 Adjusting rod    -   59 Adjusting nut    -   60 Cam device    -   61 Adjusting lever    -   62 Thrust bearing    -   63 Head portion    -   64 Male screw portion    -   65 Drive-side cam    -   66 Driven-side cam    -   67 Front-side large-diameter tubular portion    -   68 Connecting portion    -   69 Rear-side shaft    -   70 Front-side shaft

The invention claimed is:
 1. A steering column comprising: a tubularouter column; a tubular inner column internally fitted and supportedinside the outer column; and a column-side bracket fixed by welding toan outer-circumferential surface of the outer column; the outer columnhaving a press-fitted portion into which the inner column ispress-fitted to an inner-diameter side; and an inner-circumferentialsurface of the press-fitted portion and an outer-circumferential surfaceof the inner column coming in contact with each other with aninterference fit directly or via another member only at a plurality ofcontact locations separated in a circumferential direction; wherein thecolumn-side bracket includes: a connecting plate portion, a pair of sideplate portions bent in a vertical direction from both end portions in awidth direction of the connecting plate portion and sandwiching theouter column from both sides in the width direction, and two pair offixing plate portions respectively bent toward the inside in the widthdirection from a front-end portion and a rear-end portion in afront-rear direction of the pair of side plate portions, and of thecolumn side bracket, only the two pair of fixing plate portions arewelded to the outer circumferential surface of the outer column, of thetwo pair of fixing plate portions, tip edge portions of at least onepair of fixing plate portions are close to each other in the widthdirection, and tip end portions of the at least one pair of fixing plateportions are welded to the outer-circumferential surface of thepress-fitted portion at only two weld locations that are close in thecircumferential direction, and the two weld locations exist within acircumferential range located between two contact locations adjacent inthe circumferential direction among the plurality of contact locationsat positions separated in the circumferential direction from the twocontact locations.
 2. The steering column according to claim 1 whereinthe tip edge portions are close to each other in the width direction forboth of the two pair of fixing plate portions, and the tip end portionsare welded to the outer-circumferential surface of the press-fittedportion at only two weld locations that are close in the circumferentialdirection for both of the two pair of fixing plate portions.
 3. Thesteering column according to claim 1 wherein the inner column has ridgesthat protrude toward the outside in a radial direction and extend in anaxial direction at a plurality of locations separated in thecircumferential direction of the outer-circumferential surfacecorresponding to the plurality of contact locations, and only a portionof the outer-circumferential surface of the inner column correspondingto the top portions of each of the ridges comes into contact with theinner-circumferential surface of the press-fitted portion with aninterference fit.
 4. The steering column according to claim 1 wherein aminute gap is provided between each of upper-side portions of the pairof side plate portions and the outer peripheral surface of thepress-fitted portion in a state of the steering column alone.
 5. Thesteering column according to claim 1 wherein each of the pair of sideplate portions has an offset portion in an intermediate portion in thefront-rear direction of a portion on an opposite side to the connectingplate portion in the vertical direction that is offset toward the insidein the width direction with respect to a surrounding portion thereof. 6.The steering column according to claim 1 wherein the connecting plateportion has a reinforcing rib extending in the width direction.
 7. Thesteering column according to claim 1 wherein the column-side bracket ismade of a metal plate, and a difference between a thickness dimension ofthe metal plate of the column-side bracket and a thickness dimension ofthe press-fitted portion is 30% or less the thickness dimension of thepress-fitted portion.
 8. The steering column according to claim 1,wherein the circumferential range in which the two weld locations existis 30° or less when represented by a center angle centered on a centeraxis of the outer column, and the space in the circumferential directionbetween the two weld locations is 15° or less when represented by thecenter angle.
 9. A steering device comprising: a steering column, avehicle-body-side bracket, and a clamp mechanism; wherein the steeringcolumn includes the steering column according to claim 1; thevehicle-body-side bracket has a pair of support plate portions thatsandwich the outer column and the column-side bracket from both sides inthe width direction, and a tilt adjustment elongated hole formed in eachof the pair of support plate portions and extends in the verticaldirection, and is able to be supported by the vehicle body; and theclamp mechanism has an adjusting rod that is inserted in the widthdirection through the respective tilt adjustment elongated holes of thepair of support plate portions and the column-side bracket, and a pairof pressing portions that are arranged at both side portions in theaxial direction of the adjusting rod that protrudes toward the outsidein the axial direction of the pair of support plate portions, and thatby expanding or contracting the distance in the width directiontherebetween, are able to expand or contract the distance in the widthdirection between the pair of support plate portions.
 10. The steeringdevice according to claim 9, wherein the inner column is arranged on thefront side of the outer column, and is supported with respect to thevehicle in a state in which displacement toward the front is prevented.11. The steering device according to claim 9, wherein a minute gap isprovided between each of upper-side portions of the pair of side plateportions and the outer peripheral surface of the press-fitted portion,and in a state that the distance in the width direction between the pairof pressing portions is shortened, the minute gap provided between eachof the upper-side portion of the pair of side plate portions and theouter peripheral surface of the press-fitted portion disappears, and theupper-side portions of the pair of side plate portions come in contactwith the outer peripheral surface of the press-fitted portion.